This document discusses various topics related to air pollution including: 1. It defines air pollution and lists some common air pollutants like nitrogen dioxide, sulfur dioxide, and particulate matter. 2. It explains the greenhouse effect and how increased greenhouse gases like carbon dioxide are leading to global warming and rising sea levels. 3. It describes acid rain and how emissions of sulfur and nitrogen oxides react with water vapor in the air to form acids that fall as acid rain.

1. Chapter 3
Atmospheric pollution
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2. Introduction
 Air pollution means any solid, liquid or gaseous
substances present in the atmosphere in such
concentrations that may tend to be injurious or harmful to:
Human beings
Living creatures
Plants
Property
Enjoyment

3. Why the air pollution matters more than the other forms of
pollution?
 B/c an average adult consumes 12 Kg of air per day
which is about 12 times more than the food
consumption.
 Secondly in extreme cases it proves fatal quickly
where as generally the other pollutions like soil or
water pollutions act slowly.

4. Pollution prevention
 Pollution prevention is the elimination or prevention of
wastes (air emissions, water discharges, or solid/hazardous
waste) at the source. In other words, pollution prevention
is eliminating wastes before they are generated.
 It is an approach that can be applied to all pollution
generating activity.
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5. Air pollution prevention strategies - Benefits
economic benefits and continued protection to
environment
save money for treatment and disposal costs
increase company productivity
reducing the amount of raw materials
reduce air emissions
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6. Pollution Prevention Act
 The Pollution Prevention Act defines pollution prevention as
source reduction.
 pollution should be prevented or reduced at the source whenever
feasible (i.e., source reduction).
 Pollution that cannot be prevented should be recycled in an
environmentally safe manner whenever feasible.
 Pollution that cannot be prevented or recycled should be treated in
an environmentally safe manner whenever feasible, and
 Disposal or other release into the environment should be
employed only as last chance and should be conducted in an
environmentally safe manner
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7. Pollution control Strategies in industry
The first stage in pollution control is source reduction and the
second stage is using pollution control technology. The source
reduction includes
 product changes - design, composition of materials, recycle and reusing
materials, minimizing packaging, reusable materials for consumers, and
producing more durable products
 input material changes - material substitution using less hazardous
 equipment and process modification - changing process flow, modifying
process equipment, changes operations conditions
 good operating practice - employee training, performing good material
handling, preventing loss of materials, using standard operation
procedures, performing preventive maintenance, turning off equipment not
in use, reuse, and recycle
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8. Emissions and Control Technology
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categories of air pollutants

9. CLASSIFICATION OF POLLUTANTS
 There are two basic categories of contaminants in the
ambient air; Criteria Pollutants and Non- criteria
Pollutants.
 Criteria air pollutants are those air contaminants for
which numerical concentration limits have been set as the
dividing line between acceptable air quality and poor or
unhealthy air quality
 The criteria air pollutants include four gases and two
solids:

10. Cont…
 The criteria pollutants are;
1. Nitrogen dioxide(NO2)
2. Sulfur dioxide(SO2)
3. Carbon monoxide(CO)
4. Ozone(O3)
5. Particulate matter(PM10)
6. Lead(Pb)

11. Cont…
 The Non- criteria Pollutants are those contaminants
designated as toxic or hazardous by legislation or
regulation.
 In the ambient air, non criteria pollutants tend to be several
orders of magnitude lower in concentration than the
criteria pollutants.

12. Cont…
Air pollutants can be classified as;
1. Natural Contaminants
2. Aerosols
3. Gases

13. Cont…
1. Natural Contaminants
 Pollen;
Is important natural contaminant
It causes irritation and allergy leading to
bronchitis, asthma and dermatitis.
 The air transported pollen grains range mainly
between 10 and 50 microns.

14. Cont…
2. Aerosols:
Are the dispersion of solid or liquid particles of
microscopic size in the air.
It is colloidal system in which the dispersion
medium is gas and the dispersed phase is solid or
liquid.
The term aerosol is applicable until it is in
suspension and after settlement it is no longer an
air pollutant.
 May range from 0.01 (or less) micron to 100
micron.

15. Cont…
 The various Aerosols are
Dust:
Produced by the crushing, grinding and natural
sources like windstorms.
Smoke:
Made up of finely divided particles produced by
incomplete combustion containing carbon particle.
Mists:
Is a dispersion of minute water droplets suspended
in the atmosphere

16. Cont…
 Fog:
Is dispersion of water or ice near the earth’s
surface reducing visibility
 Fumes:
Solid particles generated by condensation from the
gaseous state after volatilization from melted
substances.

17. Cont…
3. Gases; main air pollutants
 Sulphur dioxide; SO2
 It is a major air pollutant gas produced by the combustion
of fuels like coal for source of electricity production
 Oxides of nitrogen: NOX
 Oxides of nitrogen are produced either in the production
of nitric acid or in the automobile exhausts and as the
effluent of power plants.
 Out of the seven oxides of Nitrogen (N2O, NO, NO2,
NO3, N2O3, N2O4, N2O5) only nitric oxide and nitrogen
dioxide are classified as the main pollutants.

18. Cont…
 Carbon monoxide; CO
 It is produced because of the incomplete
combustion of coal and other petroleum products.
 It is produced in the exhaust of automobiles.
 Hydrogen sulphide: H2S
 H2S is an obnoxious (bad smelling) gas.
 It is produced mainly by the anaerobic (in
absence of air) decomposition of organic matter.
 Other air polluting sulfur compounds are methyl
mercaptan (CH3SH) and dimethyle sulphide
(CH3SCH3) etc

19. Cont…
 Hydrogen fluoride; HF
 It is produced in the manufacturing of phosphate
fertilizers.
 Chlorine and hydrogen chloride:
 It is mixed in the air either from the leakages
from water treatment plants or other industries
where it is produced or used.
 Hydrogen chloride is also evolved in various
industrial chemical processes.
 The main effect of chlorine is respiratory
irritation which may be fatal.

20. Cont…
 7. Ozone; O3
It is a desirable gas in the upper layers of atmosphere as it
absorbs the UV radiation of sunlight.
But near the earth surface it makes poisonous chemicals by
photochemical reactions.
 8. Aldehydes:
They are produced by the incomplete oxidation of motor
fuels and lubricating oil.
They may also be formed because of photochemical
reactions.
Formaldehydes are irritating to the eyes

21. Primary air pollutants
 Primary air pollutants are those that are emitted directly from
identifiable sources
Fine suspended particulate matter (<100μ) and
 Coarse suspended particulate matter (>100μ)
Oxides of sulfur
Oxides of nitrogen
Carbon monoxide
Halogens
Organic compounds
Radioactive compounds

22. Secondary air pollutants
Secondary air pollutants are those that are
produced in the air by the interaction of two
or more primary air pollutant.
Ozone
PAN (peroxi acetyle nitrate)
Photochemical smog
Acid mists

23. Cont…
 Smog is the most important and dangerous one out of
the above.
 Smog is a mixture; (smoke + fog)

24. Cont…
 Another way of classification of air pollutants is the
source being stationary or mobile.
I. Point source (large stationary source as power
plants)
II. Area source (small stationary sources like
residential heating)
III. Mobile source (line source like highway vehicles or
area source like Aircraft at airports)

25. Environmental Problem of Air Pollution
Global warming
Acid rain
Ozone depilation
Noise pollution

26. GREENHOUSE EFFECT & GLOBAL WARMING
 The sun shines at a high temperature i.e. about 6000K
 The solar radiation at this temperature is short-wave
radiation which can pass through the glass.
 If there is a glass chamber the solar radiation comes
through the glass and heats up the belongings inside.
 These heated up air or the other belongings radiate heat
as the long wave radiation.
 Glass is opaque to the long wave radiation and thus it
does not allow the inside heat to go out.

27. Cont…
 Thus the temperature of that house keeps on
increasing
 This is known as the greenhouse effect.
 CO2 plays the same role in atmosphere.
 It allows the short-wave radiation of sun but does not
allows the earth’s long wave radiation to escape.
 CO2 is a very useful gas as it keeps the earth warm
otherwise the temperature of earth would have been
negative and the present life would have not been
there.
 But the increasing concentration of CO2 is increasing
the temperature of the earth to a harmful level.

28. Cont…
 This warming of the earth-atmosphere system which
enhanced by greenhouse effect is called global
warming.
 The increasing temperature is substantially increasing
the melting of ice on poles and other glaciers.
 This higher melting of ice is shortening the glaciers,
flooding the rivers and increasing the levels of seas and
oceans.
 There is a danger that these increased levels shall
submerge some places within a short time to come

29. Cont…
 The increased temperature increases different vector
borne diseases like malaria etc.
 The increased temperature is very much
uncomfortable and requires more electricity for
cooling.
 If the current trend of increase in the greenhouse
gases continues it shall make the earth hell.

30. Cont…
 Human activities altered the composition of gases in the atmosphere
are;
Fossil fuel combustion,
Deforestation,
Agriculture and
Large-scale chemical production
 These alterations have caused a warming of the earth-atmosphere
system by enhancement of the greenhouse effect.

31. ACID RAIN
 The gaseous air pollutants like SOX and NOX are
common in atmosphere
 CO 2 is always present in the atmosphere as a natural
constituent.
 When the rain fall occurs it dissolves the CO 2 present
in the air and makes the carbonic acid.
 This makes the rain slightly acidic and reduces its pH.
 Due to industrialization and the automobile exhaust
SOX and NOX are present in the air in large quantities.
 They react with the moisture to form sulfuric and nitric
acids they make such rain as acid rain

32. Cont…
 This acid rain strongly harms every where and
everybody, may it be a building, human beings,
animals, plants, the fresh bodies of water or the soil.
 High acidity kills the fish and other aquatic animals
and plants.
 Green algae and many useful bacteria are killed due
to acidity.
 The killed organism and destroyed plants increase the
organic matter

33. Cont…
 Acid rain adversely affects the soil and the
vegetation.
 As it accelerates the leave surface erosion the growth
of plants is hampered and the trees are badly affected.
 As we know that the trees reduce the CO2 and
increase the O2 they are our life supporting systems.

34. Cont…
 The acid rain can be reduced by
Using low sulfur coal
Gasification
Alternative fuel to coal
Alternative methods of power generation like the
renewable sources of energy, like solar, wind, hydro-
electrical, biomass etc.

35. OZONE DEPLETION
 Ozone is harmful gas near the earth surface (photo
toxic) and it is very useful in the upper layers of the
atmosphere (stratosphere).
 90% of the ozone is concentrated in the stratosphere
and absorbs 95% of the UV radiation.
 It is useful gas there, as it absorbs the ultraviolet
portion of the solar radiation which is very much
harmful to human beings.
 UV reaching the earth produces skin cancer and other
diseases.

36. Cont…
 Because of the air pollution this ozone layer is depleting
and wherever the concentration becomes very low it is
termed as ozone hole.
 The following three constituents are mainly responsible
for the depletion of stratospheric ozone

37. Cont…
 Nitric oxide molecules:
Nitric oxide reacts with ozone to make nitrogen
dioxide which in turn reacts with atomic oxygen
to produce nitric oxide again
NO + O3 = NO2 + O
NO2 + O = NO + O

38. Cont…
 Chlorine atom:
Chlorine atom reacts with ozone to give chlorine
monoxide which reacts with atomic oxygen to
regenerate chlorine atom again
Cl + O3 = ClO + O2
ClO + O = Cl + O2
 Hydroxyl ion:
The photo dissociation of water molecules produces
hydroxyl ion which reacts with ozone molecule to
produce HO2 which reacts with another ozone
molecule to give again the OH molecule
OH + O3 = HO2 + O2
H O2 + O3 = OH +2O2

39. Causes of the Ozone Layer Depletion
1. Use of chlorofluorocarbons: The CFCs are
responsible for maximum damage to the ozone layer
2. Nitrogenous fertilizers: Bacterial action on
nitrogenous fertilizers produces nitrous oxide which
escapes into atmosphere and gets accumulated as its
decomposition is difficult.
3. Supersonic transport: Supersonic jetliners, rockets
and space shuttles discharge various oxides of
nitrogen, carbon, hydrocarbons to attack the O2.
4. Nuclear tests: Huge quantity of gases are released
in the nuclear explosions which damage the ozone
layer

40. Effects of Ozone Layer Depletion
 As the concentration of ozone reduces in the protective layer
the harmful ultraviolet radiation (UV-A, UV-B and UV-C)
shall reach the earth surface and shall cause many diseases like
the following:
1. Skin cancer of various types About 1 lac people die from
this disease.
As an estimate the cases of skin cancer are doubled with a
25% reduction in ozone layer.
2. The ultraviolet radiation directly increases the cataract
(disease of eyes).
3. The UV radiation affects the eyes of wild life also and as
they cannot protect themselves this effect is more
pronounced.
4. The depletion of ozone lead to increased photochemical
smog and degradation of outdoor paint and plastic.

41. Pollution Control Technology
Cyclone
Electrostatic precipitator
Adsorption tower
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42. Adsorption Towers
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Adsorption towers consist of cylinders packed with the
adsorbent.
The adsorbent is supported on a heavy screen
Since adsorption is temperature dependent, the flue gas is
temperature conditioned.
Vapor monitors are provided to detect for large
concentrations in the effluent.
Large concentrations of the pollutant in the effluent
indicate that the adsorbent needs to be regenerated.

43. Cont…
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44. Cyclone
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The particles are removed by the application of a
centrifugal force.
The polluted gas stream is forced into a vortex
The motion of the gas exerts a centrifugal force on the
particles, and they get deposited on the inner surface of the
cyclones

45. Cont…
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46. Cont…
 The gas enters through the inlet, and is forced into a spiral.
 At the bottom, the gas reverses direction and flows
upwards.
 To prevent particles in the incoming stream from
contaminating the clean gas, a vortex finder is provided to
separate them.
 The cleaned gas flows out through the vortex finder.
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47. Electrostatic Precipitator (ESP)
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The particles in a polluted gas stream are charged by
passing them through an electric field.
The charged particles are led through collector plates
The collector plates carry charges opposite to that on the
particles
The particles are attracted to these collector plates and are
thus removed from the gas steam

48. 48
Cont…

49. Cont…
Charging Electrodes in the form of thin wires are placed in
the path of the influent gas.
The charging electrodes generate a strong electric field,
which charges the particles as they flow through it.
The collector plates get deposited with the particles.
The particles are occasionally removed either by rapping
or by washing the collector plates.
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